This invention relates to opening rollers for open-end spinning machines.
In open-end spinning machines, a sliver of fibres is separated into individual fibres. The separate fibres are then fed in parallel alignment into a rotating spinning chamber which twists together the fibres to form a yarn which is drawn from the spinning chamber.
The separation of the sliver into individual fibres is carried out on a so-called beater or opening roller which conventionally comprises a cylindrical or conical surface carrying an array of sharp projections. The sliver is fed at a controlled rate on to the rotating opening roller so that the projections dislodge the individual fibres from the sliver, arrange them in parallel alignment, and transfer the fibres into the spinning chamber.
The projections on the surfaces of opening rollers have taken the form of either saw-tooth edges wires wound helically onto the drum, or of arrays of pins projecting from the surface of the drum. Where the drum includes a pinned surface, the pins are usually arranged in axial rows forming a series of repeating patterns.
In order to ensure that the pins of each pattern engage a different point on the sliver as the pins are moved relative to the sliver, each pattern of pins is composed of a series of parallel helical lines one of which extends from the first pin in the first row of the pattern to the second pin in the first row of the adjacent pattern. Consequently, all the pins in each pattern are arranged on different circumferential circles on the surface of the drum.
With these pinning arrangements however, there is a tendency for the fibres to be driven axially of the roller by the helical lines of pins causing bunching and, consequently, poor separation of the fibres, towards one end of the roller.